The present invention relates generally to the art of gas pressure driven fluid pumps. More particularly, the invention relates to such a pump utilizing a snap-acting rotary valve to control gas ports.
Condensate removal systems in steam piping arrangements often utilize gas pressure driven pumps that function without electrical power. As described in U.S. Pat. No. 5,938,409 to Radle (incorporated herein by reference), such a pump will typically have a tank with a liquid inlet and liquid outlet. The liquid inlet and liquid outlet, which are located near the bottom of the tank, will be equipped with an inlet check valve and an outlet check valve to permit liquid flow only in the pumping direction. A pair of valves interconnected by a snap-acting linkage control a gas motive port and a gas exhaust port.
The pump operates by alternating between a liquid filling phase and a liquid discharge phase. During the liquid filling phase, the motive port is closed while the exhaust port is open. A float connected to the snap acting linkage rises with the level of liquid entering the tank. When the float reaches an upper crossover point, the linkage snaps over to simultaneously open the motive port and close the exhaust port. As a result, the pump will switch to the liquid discharge phase.
In the liquid discharge phase, steam or other motive gas is introduced into the pump tank through the motive port. The motive gas forces liquid from the tank, thus causing the float to lower with the level of the liquid. When the float reaches a lower crossover point, the linkage snaps over to simultaneously open the exhaust port and closes the motive port. As result, the pump will again be in the liquid filling phase.
While the snap acting linkage used in gas pressure driven pumps of the prior art has generally functioned well, there exists room in the art for additional snap acting valve arrangements.